Field of the Invention
The invention relates to a method for connecting a field device to an operating unit. The invention further relates to a field device.
Description of Related Art
In process automation, processes or media are monitored by field devices in the form of measuring devices (sensors) or influenced by field devices in the form of regulator control elements (actuators). These field devices are often directly or indirectly connected to control rooms or process control systems.
In order to be able to directly access a field device, so-called handhelds are often used as mobile operating units, see, e.g., DE 10 2005 041 862 A1. A status display of a field device, which is triggered by a radio signal, consists, for example, of a blinking signal or an acoustic signal, see, DE 103 26 627 A1 and corresponding U.S. Patent Application Publication 2005/0030161 A1. Using corresponding passwords and assigned rights, it can also be thereby provided that access is only allowed for certain parameters of the field device, see, e.g., DE 10 2012 109 348 A1.
The connection between operating unit and field device occurs, for example, for the parameterization, the request for status information or for diagnostic purposes. In general, communication between the operating unit and the field device is implemented via the connection.
It is recommended in respect to wireless networks in DE 10 2004 055 308 A1 and corresponding U.S. Patent Application Publication 2008/0299915 A1 that the device name, a TAG number or a serial number is used for identification of the field device. The TAG number thereby also indicates the location of the field device within the processing system.
One possibility for communication between devices is BLUETOOTH®. A first establishment of a connection between two BLUETOOTH® devices is thereby called pairing. A link key results from specifications transmitted between the devices, which allows subsequent connections to occur automatically.
After being put into the active state, BLUETOOTH® devices are registered with a MAC address (media access control address) and listen automatically for messages in the standby mode. The devices are identified with an identification name. In order to authorize a connection, it is generally necessary to enter an assigned passkey. Examples of how to use this passkey or password can be taken, for example, from WO 02/056536 A1.
It can be a problem when the field device is mounted at a location in the processing system that is awkward or very difficult to access for the user. Examples of this are measuring devices on high tanks, or valves within an arrangement of tubes, etc. Field devices can also be partly mounted on the ceiling or in ducts. The ambient conditions, for example when the field device is located directly in the process, can also be unpleasant for an operator. It is also a problem when direct visual contact with the field device cannot be established or can only be established with difficulty. Especially if several BLUETOOTH® field devices are located near one another under such conditions, it can be difficult to identify which field device is addressed or which identification name belongs to which device.